1. Field of the Invention
This invention relates to computing systems, and more particularly, to efficient reporting of power usage.
2. Description of the Relevant Art
The power consumption of modern integrated circuits (IC's) has become an increasing design issue with each generation of semiconductor chips. As power consumption increases, more costly cooling systems such as larger fans and heat sinks must be utilized in order to remove excess heat and prevent IC failure. However, cooling systems increase system costs. The IC power dissipation constraint is not only an issue for portable computers and mobile communication devices, but also for high-performance microprocessors, which may include multiple processor cores, or cores, and multiple pipelines within a core.
High-performance microprocessors may be placed in servers, which may be grouped together in a server room such as a data center. Server racks within a data center comprise expensive hardware configured to store data, perform user requested transactions, and safeguard both the data and the processing of transactions. Cooling the server racks includes complex solutions and advanced cooling technology. For portable computers and servers, the cost of cooling systems may be reduced if the cooling system is able to dynamically adjust to a machine's current power usage. For example, an air conditioner may be adjusted for a data center to run at less than full capacity all day each day if an accurate report reliably communicates the power usage of the machines within the data center. Similarly, the cooling strategies may be adjusted on a timely basis or indefinitely changed when accurate power usage numbers are reported. Further, cooling strategies may also dynamically change within a portable computer if accurate power usage numbers are reported. f
It may be difficult to obtain an accurate report of a given machine's power usage. Current methods for reporting power usage to software or an external agent such as a rack controller are not reliable or accurate. For example, both analog and digital thermal sensors may be placed throughout a semiconductor chip die. The thermal sensors provide information as to when the die heats up in a particular area due to increased compute activity. These thermal sensors rely on correlating temperature with power consumption. However, these sensors respond to each change in temperature whether it's driven by a compute-related boost in power consumption or by an external environmental factor, such as a rise in ambient temperature. In addition, there is a time delay between a compute-related boost in power consumption and a temperature increase. Further, analog current sensors that measure an amount of current drawn by circuits on a die typically have a large inaccuracy associated with readings. Also, these sensors report a current usage for a set of multiple cores rather than for each core individually. Therefore, it may be difficult to know if any and which of the cores has entered a compute-related boost in power consumption. Further still, available digital power monitors report current values for operating frequency, operational voltage, utilization and possibly a battery meter, but these values do not directly report a wattage value for power consumption.
In view of the above, efficient methods and mechanisms for efficient reporting of power usage are desired.